What Causes Sand Mound Wet Spots?

A sand mound system is very similar to a conventional septic system, which consists of a septic tank and a soil absorption system. Sewage solid settles in the septic tank while the effluent goes to the soil absorption system, known as the sand mound, where it is treated and disposed of. Before setting up and designing a sand mound system, the ground is tested first for its soil absorption rate. The process is called a “perc” test or percolation test. A soil with high absorption rate is not ideal for a standard soil absorption system, especially if the liquid drains the water too fast before it could properly pre-treat the effluent. And that is where a mound system is being used. A mound system is an alternative for a soil absorption system for areas with aberrant soil conditions.

There are cases, however, wherein wet spots can be seen on a sand mound. This may indicate potential problems on the system. Those puddles that are formed near the ground surface of the system are called wet spots. This happens when water is not able to pass through the mound system properly, so it backs up into the home or it is forced to the surface, eventually creating puddles.

The most common cause of sand mound wet spots is oil and grease that build up in the soil. Normal amounts of bacteria or microbes cannot rapidly digest oil and grease that goes to the system. Once these materials leave the septic tank, they will stay in the sand mound where they congregate. Over time, these materials build up in the soil until they clog the drainage. When this happens, water must eventually find a different path. Using a biological additive – those that are made up of bacteria, yeast and enzymes – is proven to reduce oil and grease.

Overloading the septic system with water may also result to failure of the sand mound. A sand mound’s size is decided according to the usual water consumption/usage in a household, or even more. Obviously, the system will not work properly if it receives more than water that it can handle.
Similar to septic tanks, using harsh chemicals on the system also harms the sand mound. These harsh chemicals destroy the bacteria needed to break down scum in the wastewater. This condition of the septic system is known as the “die-off” condition. This happens when a homeowner uses bleach and other anti-bacterial agents resulting to elimination of necessary bacteria in the system. Using additives may restore the system’s condition by reducing the amount of out-flowing solids in the septic tank.

Poor construction also causes sand mound failure. Some designers do not consider the location and condition of the site before installing the mound system. When constructing mounds, the contour of the existing ground should be followed. Mounds may not look very pretty because of the hump, but it could be constructed to complement your house’s landscaping design. Also, it is not ideal to place a mound in a lower area where water may stack up.

It is your duty to maintain the sand mound system to avoid wet spots. This maintenance should include pumping the system as needed and visually inspecting the internal and external components. Have the system checked out every few years or as suggested by the manufacturer. It is also helpful to conserve water and install water saving devices at home. The use of additives can help resolve the oil and grease issue in the septic system when used properly. Commercial grade additives can reduce the load put on the sand mound and help keep wet spots away.

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